This invention relates to an automatic developing apparatus which carries out the precise development of a resist deposited on a semiconductor substrate to be processed.
The formation of a resist pattern on a photomask or semiconductor wafer is generally performed by the lithographic process. The lithographic process comprises the steps of applying a resist material to the surface of a substrate to be processed, drawing an image, by means of selective impingement of electromagnetic rays such as ultraviolet rays or particulate rays, for example, electronic rays, on the resist, and developing the resultant patterned resist.
This development method is basically classified into three types:
Dipping process PA1 Spray process PA1 Paddle process
The dipping process consists in dipping an object substrate, coated with a resist, in a developing solution. This process has the merits in that only a small amount of developing solution needs to be used; the temperature of the developing solution is easy to control; and a resulting resist pattern exhibits relatively small dimensional variations. However, the most noticeable drawbacks of the dipping process are that when development is carried out continuously, to process a plurality of substrates, floating foreign particles noticeably appear in the developing solution; the settling of these foreign particles tends to give rise to defects in the resist pattern, interconnection breakages, or short-circuiting, thereby presenting difficulties in the formation of a predetermined resist pattern; the subject-developing process is lowered in operability and presents difficulties with regard to automation; further, while the processed substrate is moved out after development of the resist pattern, the undesirable dissolution of the finished resist pattern is advanced by the developing solution adhering thereto; it is therefore impossible to fully meet the present-day demand for a higher-precision resist pattern.
The spray process consists in spraying a clear developing solution on a resist formed on the substrate. The spray process offers the advantages in that the developing step can be easily automated; since a clear developing solution is always applied, a finished resist pattern is less subject to defects. But the spray process is accompanied with the drawbacks in that the temperature of the developing solution is difficult to control; since differences appear in the temperature of the developing solution applied to the surface of the substrate, due to the effect of vaporization heat, the finished resist pattern tends to undergo dimensional variations.
The paddle process comprises the steps of keeping an object substrate, coated with a resist, in a resting state, or in a slowly rotating state, and forming a film of a developing solution over the resist, by means of dripping. The paddle process is an intermediate method between the spray process and the dipping process. Namely, the paddle process offers the advantages in that the consumption of developing solution is low, as in the case of the dipping process and that automation is easily realized. Still, the paddle process is accompanied with the drawbacks in that the temperature of the developing solution is difficult to control, as in the case of the spray process; and dimensional variations in the resulting resist pattern tend to be noticeable.